Heating, ventilation, and air-conditioning (HVAC) modules for automotive applications are known to use centrifugal blower assemblies. A centrifugal blower assembly typically includes an impeller disposed within a blower housing. The impeller is defined by a hub having a series of radially disposed and axially extending fan blades. An air flow space is defined between the outer edges of the fan blades and the interior surfaces of the blower housing. The shaft of an electric motor is attached to the center of the hub and the motor is operative to rotate the impeller at varying speeds. The electric motor rotates the blower at a predetermined speed causing the fan blades to pull in outside air in an axial direction toward the center of the blower housing and then forces the air radially outward out of the blower housing and through the HVAC module.
At certain speeds of rotation of the impeller during normal operation, a large sector of fan blades may be subjected to blade stall, resulting in reduced blower efficiency. During stall conditions, the air flow separates from the fan blades resulting in eddies downstream close to the impeller hub and upstream close to the fan edges. The reversing of the air flow through stalled blades results in turbulent flow and significant noise production
Based on the foregoing, there is need for centrifugal blow assembly that has a reduced susceptibility for stall conditions, greater efficiency of energy transfer, and lower noise generation.